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Cold temps have little effect on insect pests

By DEBBIE BEHRENDS-
dbehrends@shawmedia.com

Feb. 7, 2014

AP file photo

Caption

Frigid temperatures in the Midwest are having little effect on many insects that bug us, including emerald ash borers, according to entomologists. Temperatures would need to be in the single digits with no snow cover to have any effect on the pests.

Although the below-zero temperatures are difficult for humans and their pets to endure, entomologists report they have little effect on the insects that bug us.

Scott Schirmer, emerald ash borer specialist with the Illinois Department of Agriculture, said that particular pest overwinters as a larva. The emerald ash borer, an invasive species from China, is blamed for killing many area ash trees.

“Don’t count on the weather to have an significant impact,” Schirmer said. “It will knock down a small percentage, but we can expect to continue managing EAB.”

Schirmer said the drought of 2012 had a bigger, and more negative impact, because the trees were stressed by the lack of water.

On the agricultural front, Russ Higgins, a University of Illinois Extension educator for commercial agriculture, said the temperature has little effect on insects that overwinter as eggs or larva. The only insects he could think of that overwinter as adults are the bean leaf beetle and the alfalfa weevil – neither of which are prevalent in the area.

“In our general area in northern Illinois, our big insect pest is the corn rootworm beetle,” Higgins said. “Mike Gray [U of I entomologist] did some research on the subject. Unless it was really cold – by that I mean temperatures in the single digits with no snow cover – rootworm populations were not reduced.”

Higgins said snow cover provides an insulating blanket for insects.

To illustrate that, he said one recent morning at the Northern Illinois Agronomy Research Center near Shabbona, when the air temperature was 15 below, the soil temperature just four inches below the surface was 29.6 degrees.

That insulation has been good for small wildlife, as well, according to Peggy Doty, Extension educator in energy and environmental stewardship.

“There are probably some things out there that the cold is helping to kill, but small critters – mice, voles, shrews – are doing awesome,” Doty said. “They are tunneling around under the snow.

“You have to remember that just one crumb of bread is a full belly for a field mouse,” she said.

The scavengers, animals like raccoons and opossums, aren’t doing as well because finding food is more difficult for them, Doty said.

The snow providing insulation for the wildlife today also will help replenish the depleted water table as it melts, Shirmer said.

Doty agreed.

“It can’t hurt. It’s dry snow, but it’s still moisture. It can make a difference.”

The way the snow melts will make a difference, too.

“If – and I say if – it melts slowly, it’s a huge gift,” she said.

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